Welcome to the second part of the “PHP’s Source Code For PHP Developers” series.In the previous part ircmaxell explained where you can find the PHP source code and how it is basically structured and also gave a small introduction to C (as that’s the language PHP is written in). If you missed that post, you probably should read it before starting with this one.What we’ll cover in this article is locating the definitions of internal functions in the PHP codebase, as well as understanding them.How to find function definitionsFor a start, let’s try t...